The ability to generate a coherent soap bubble with reliability over a range of flow rates, particularly at high gas flow rates, is a major limitation of prior art flowmeter designs. In applicant's parent application, as above identified, a flowmeter is described incorporating a bubble generator which forms a bubble at the mouth of the flowtube. The bubble generator includes an opening in the flowtube in combination with a shutter to control the size of the opening. The arrangement operates as a variable bypass for air flow. The size of the opening in the flowtube is varied based upon the rate of gas flow to be measured.
The present invention is directed to other embodiments for generating a coherent soap bubble in the flowtube and offers advantages in simplicity of design and manufacture over the bubble generating arrangements taught in the parent application.